//https://leetcode.cn/problems/univalued-binary-tree/

bool isUnivalTree(struct TreeNode* root) {
    if (root == NULL)
    {
        return true;
    }

    if (root->left && root->left->val != root->val)
        return false;

    if (root->right && root->right->val != root->val)
        return false;

    return isUnivalTree(root->left) && isUnivalTree(root->right);

}